What makes a website responsive?

A responsive website adapts its layout, typography, images, and interactive elements to work well at any screen size. Key elements include a viewport meta tag, flexible grid layouts (CSS Flexbox or Grid), responsive images with srcset, touch-friendly tap targets (44px minimum), and readable text without zooming. Viewpo tests for all of these automatically.

Why do some responsive test tools show blank pages?

Most free responsive test tools use iframes to embed your site at different sizes. Modern websites block iframe embedding with X-Frame-Options or Content-Security-Policy headers for security. When a tool tries to embed a site that blocks iframes, you see a blank page or a "Refused to display" error. Tools like Viewpo avoid this by using real browser rendering instead of iframes.

Is Viewpo free to use?

Yes. Viewpo's free tier includes 50 audits per month with real browser screenshots at 3 viewport sizes and A-F grading. No credit card or account required for basic audits. Paid plans start at $19/month for more audits, more viewports, and API access.

Test if your website is responsive. Instantly, for free.

Paste your URL and see exactly how your site looks on phones, tablets, laptops, and desktops. Get an A-F grade with specific issues to fix — not just screenshots.

What to look for in a website responsive test

Key criteria for choosing the right tool — and how Viewpo stacks up.

Instant results

A good responsive test should work immediately — paste a URL and get results. No accounts, no extensions, no downloads.

Viewpo runs in your browser. Paste a URL, get screenshots and a grade in seconds. No sign-up needed.

All screen sizes at once

Resizing your browser window only shows one size at a time. A proper test shows phone, tablet, and desktop together.

Viewpo renders your site at 375px, 820px, 1440px, and 1920px simultaneously with real screenshots.

Issue detection, not just preview

Seeing your site at different sizes isn't enough. You need to know what's broken and where.

Viewpo detects overflow, touch targets, contrast, images, and accessibility issues — and explains each one.

Works on every website

Many responsive test tools use iframes, which fail when sites set X-Frame-Options or CSP headers. That's most modern websites.

Viewpo uses real Chromium rendering. No iframes, no embedding — it works on every site, including those with strict security headers.

Why "responsive" is more than "fits on a phone"

A website that technically fits on a phone screen isn't necessarily responsive. True responsiveness means text is readable without zooming, buttons are large enough to tap with a thumb, images scale properly without overflowing the viewport, and the layout adapts meaningfully to each screen size. Many sites pass a basic mobile check but fail on real-world usability — a product grid that squeezes into a single column, a navigation menu that overlaps content, or a form where the submit button is half off-screen. Viewpo catches these issues because it renders your site in a real browser and runs automated checks at each viewport, not just a "does it fit?" test.

Browser resize vs dedicated testing tools

The simplest responsive test is dragging your browser window to different widths. It's free and instant, but it has limitations: you see one size at a time (easy to miss issues at specific breakpoints), there's no record to share with teammates, and you're relying on your own eyes to spot problems. Dedicated tools like Chrome DevTools device mode give you preset device sizes but still show one viewport at a time. Viewpo shows all viewports side by side with automated issue detection, so you get both the visual overview and the specific problems — in a format you can share with a link.

What Viewpo tests at every viewport

At each screen size, Viewpo runs five categories of automated checks. Overflow detection catches elements that extend beyond the viewport width — the horizontal scroll you didn't know existed. Touch target analysis flags buttons, links, and form elements smaller than 44x44 pixels, the minimum size for reliable finger tapping. Image audits catch missing alt text and oversized images that waste bandwidth on mobile. Contrast checking identifies text that fails WCAG readability standards at different sizes. Accessibility checks catch structural issues: missing ARIA landmarks, heading hierarchy violations, and unlabelled form inputs. Every issue includes a plain-language explanation and its location on the page.

Frequently Asked Questions

Common questions about choosing a website responsive test.

The quickest way is to paste your URL into a responsive testing tool like Viewpo. It renders your site at phone (375px), tablet (820px), laptop (1440px), and desktop (1920px) sizes in a real browser and shows you screenshots alongside an A-F grade. For a manual check, open Chrome DevTools (F12), click the device toolbar icon, and cycle through preset device sizes — but you'll only see one at a time.

Read all FAQs

Try the website responsive test that grades your site

Paste any URL and get real browser screenshots at multiple viewports with an A-F responsive design grade. Free, no install.

Free during beta. Plans from $19/mo at launch — early supporters get a lifetime discount.